Numerical Calculation Of Aerodynamic Noise And Design Of Noise Reduction For High Speed Trains

With the increase of both the number of high-speed trains running in our country and the speed continuously,and the noise pollution becomes more and more serious.Especially when the speed exceeds 300 km/h,the aerodynamic noise of high-speed trains has exceeded the wheel-rail noise as the main noise source.Therefore,it is of great significance to study the producing mechanism and control of aerodynamic noise of high-speed trains.Aiming at the aerodynamic noise problem of high-speed train,a hydrodynamic model for acoustic simulation calculation of high-speed train is established.The aerodynamic drag and aeroacoustics of high-speed train are calculated and compared under the two conditions of considering track effect and not considering track effect,and the design scheme of noise reduction is rapidly evaluated based on SNR method.The main work is as follows:(1)A computational fluid dynamics model for acoustic simulation analysis of high-speed train is established.According to the geometric model of CRH3 high-speed train,the computational fluid dynamics models of high-speed train considering track effect and not considering track effect are established.The total number of elements without considering track effect is 22.9 million,and the total number of elements with track effect is 33 million.On the basis of not affecting the main structure of the model,the local complex areas such as car body,bogie,pantograph and track are simplified.The finite element model includes head car,middle car,tail car,six Bogies and pantograph.In order to make the calculation closer to the actual situation,the finite element model considering the rail effect includes the main track structures such as roadbed,rail and sleeper.(2)The aerodynamic drag and surface noise sources of high-speed trains is calculated and analyzed.Based on the standard k-ε model,the steady-state flow field outside the train at 250 km/h,300 km/h and 350 km/h running speeds is numerically simulated under the two conditions of both considering the track effect and not considering the track effect.The pressure coefficient,friction coefficient and sound power level distribution on the longitudinal symmetry plane of the train are achieved.The calculation results show that the friction coefficient is smaller when the pressure coefficient is positive and larger,and the friction coefficient is larger when the pressure coefficient is negative and smaller.The distribution law of surface acoustic power level is the same as that of surface friction coefficient.(3)The aerodynamic noise of high-speed train in far field is calculated.Taking the steady-state simulation results as the initial conditions,the transient calculation of the external flow field of high-speed train is carried out based on the large eddy simulation(LES),and the fluctuating pressure on the surface of high-speed train is obtained.Based on Lighthill’s acoustic analogy theory,the far-field aerodynamic noise with or without track effect is calculated by using of FW-H method at three speeds,and the distribution rule of the far-field aerodynamic noise and the noise frequency spectrum of monitoring points are achieved.The results show that the overall distribution of far-field aerodynamic noise and the noise spectrum change greatly after considering the rail effect.(4)SNGR method is used to evaluate the noise reduction of bogie field of high-speed train head.In order to reduce the aerodynamic noise of the bogie at head,a guide fluid guard plate is added to the bogie at head.Based on the steady flow field data of high-speed train,the near-field noise distribution characteristics and the far-field noise distribution rule of the train after a guide fluid guard plate is added are achieved by using of the SNGR method in the Actran software.The calculation results show that the aerodynamic noise at the head of the train is obviously reduced when the guide fluid guard plate is added.